Electro-pneumatic latching valve system

ABSTRACT

The electro-pneumatic latching valve system having an electrical switch unit that further includes an “apply” or “activate” switch, a “release” or “deactivate” switch, and a power supply. A first solenoid valve is in electrical communication with the activate switch and a second solenoid valve is in electrical communication with the deactivate switch. A pneumatic latching valve is in pneumatic communication with the first and second solenoid valves and a source of pressurized control and supply air is in pneumatic communication with the pneumatic latching valve and the solenoid valves. A terminal device, e.g., a spring brake, is in pneumatic communication with the latching valve, and the device is released or applied in response to pressurized supply air delivered to the device through the pneumatic latching valve in response to pneumatic control signals delivered to the pneumatic latching valve from the solenoid valves.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional of pending U.S. patentapplication Ser. No. 10/784,717 filed on Feb. 23, 2004 entitled“Electro-pneumatic Latching Valve System” which claims the benefit ofU.S. Provisional Patent Application Ser. No. 60/449,710 filed on Feb.24, 2003 entitled “Remote MV-3,” U.S. Provisional Patent ApplicationSer. No. 60/450,422 filed on Feb. 26, 2003 entitled “Remote MV-X(Provisional No. 2),” and U.S. Provisional Patent Application Ser. No.60/466,820 filed on Apr. 30, 2003 entitled “Apparatus and Method forElectro-pneumatic Air Brake System,” the entire disclosures of which areincorporated as if fully rewritten herein.

STATEMENT REGARDING FEDERALLY FUNDED RESEARCH

This invention was not made by an agency of the United States Governmentnor under contract with an agency of the United States Government.

TECHNICAL FIELD OF THE INVENTION

This present invention relates generally to braking systems forheavy-duty vehicles and more specifically to a valve system thatutilizes a combination of electronics and pneumatics to operate theparking brakes and emergency brakes of a vehicle.

BACKGROUND OF THE INVENTION

Conventional heavy-duty vehicle air brake systems typically usemechanical pneumatic push-pull control valves to control a vehicle'sparking brakes. These large, pneumatic push-pull valves are usuallyplaced within the vehicle's instrument panel, as are the pneumatic linesand connectors used to connect the brake control valves to the othercomponents of the vehicle's air brake system. Dash mounting of thesecomponents may decrease pneumatic performance while consuming criticalspace in the vehicle's instrument panel which may ultimately result indash configurations that are detrimental to the driver's comfort andconvenience. Furthermore, installation of the pneumatic instrument panelcontrols requires complex, airtight connections during the finalassembly phase of the vehicle. Thus, there is a need for a system thatremoves the pneumatic lines from a vehicle's dashboard while maintainingthe basic functions and overall characteristics of currently used brakesystems.

Some prior art braking systems have utilized electric controls toaddress the problem of limited dashboard space. Such systems typicallyinclude an electrical switch assembly mounted on or in the instrumentpanel for controlling the parking brakes with an electrically responsivevalve located remotely from the dash components. One problematic aspectof these systems is that when electrical power is lost to the valve, thevalve moves to its exhaust position, drops the parking brake linepressure to atmospheric pressure, and applies the vehicle's parkingbrake. Loss of electrical power or connectivity to a vehicle's brakesystem may be the result of loose terminal connections, broken wires, adead battery, or other unforeseen events. As will be appreciated bythose skilled in the art, inadvertent engagement of the parking brakemay create an extremely dangerous situation if the vehicle is moving atany appreciable speed. Thus, there is a need for an air brake systemthat includes the use of electronics, but that prevents the inadvertentapplication of the vehicle's parking brakes should power to the brakecontrol system be lost.

SUMMARY OF THE INVENTION

These and other disadvantages of the prior art are overcome by thepresent invention, which provides an electro-pneumatic system forcontrolling the parking and emergency brakes of a vehicle. The exemplaryembodiment shown in the Figures utilizes a series of electricallycontrolled valves that are used to operate one or more pneumaticlatching valves to apply or release a vehicle's parking brakes. Thus,the logic of this system and method of includes both electrical andpneumatic components.

The electro-pneumatic latching valve system of the present inventiontypically includes a switch unit having an electric “apply” or“activate” switch, a “release” or “deactivate” switch, and a powersupply. In accordance with an exemplary embodiment, an electro-pneumaticlatching valve unit includes a first valve is in electricalcommunication with the activate switch and a second valve is inelectrical communication with the deactivate switch. A third valve,which is referred to herein as a “pneumatic latching valve” is inpneumatic communication with the first and second valves. A source ofpressurized air is in pneumatic communication with all three valves ineach valve unit. The first and second valves deliver control air to thelatching valve in response to either an electric “apply” signal or anelectric “release” signal and the latching valve opens or closes inresponse to these signals. A terminal device, such as a spring brake, isin pneumatic communication with the latching valve and is released inresponse to pressurized supply air delivered to the device through theopen latching valve. The device is applied when the latching valvecloses and the pressurized supply air is exhausted from the devicethrough the latching valve.

In alternate embodiments of the present invention, the electro-pneumaticlatching valve system is incorporated into the parking and emergencybrake system of vehicles having the tractor and trailer configurationand vehicles having the truck configuration or mode. The electricallycontrolled valves are used only to induce a “change of state” in thevehicle's parking brakes, while the pneumatic latching valve is thesystem component that actually applies or releases the vehicle's brakes.Once the pneumatic latching valve has applied or released the parkingbrakes, any loss of electrical power to the valves or to the brakesystem, will not result in a change in the state of the vehicle'sparking brakes, i.e., will not automatically apply the vehicle's parkingbrakes. As indicated previously, this aspect of the present invention isparticular advantageous from a safety perspective.

Further advantages of the present invention will become apparent tothose of ordinary skill in the art upon reading and understanding thefollowing detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a partof the specification, schematically illustrate one or more exemplaryembodiments of the invention and, together with the general descriptiongiven above and detailed description of the preferred embodiments givenbelow, serve to explain the principles of the invention.

FIG. 1 is a schematic representation of a prior art air brake systemthat utilizes pneumatics solely to operate the braking system of avehicle.

FIG. 2 is a block diagram showing the electro-pneumatic latching valveunit of the present invention.

FIG. 3 is a schematic representation of the electro-pneumatic latchingvalve unit of the present invention incorporated into an air brakesystem for a vehicle having both a tractor portion and a trailerportion.

FIG. 4 is a schematic representation of the electro-pneumatic latchingvalve unit of the present invention incorporated into an air brakesystem for a vehicle having only a truck, bus, or non-towing vehicleportion.

FIG. 5 is a flowchart showing an alternate embodiment in which aelectronic control unit is utilized to integrate certain functions ofthe air brake system of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an apparatus for use in controlling anair brake system and other pneumatic devices. The exemplary embodimentof the present invention utilizes a series of electrically controlledvalves that are in turn used to operate at least one pneumatic latchingvalve to apply or release a vehicle's parking brakes. Thus, the logic ofthe system and method of the present invention includes both electricaland pneumatic components. The electrically controlled valves, which inthe exemplary embodiment are solenoid valves, are used only to induce a“change of state” in the vehicle's parking brakes, as described below.With reference to the Figures in general, a series of small capitalletters are used to designate the ports of the various valves includedin the system of the present invention. The letter “S” refers to“supply,” the letter “C” refers to “control,” the letter “D” refers to“delivery,” and the letter “E,” refers to “exhaust.” In the context ofthis invention, control air is used as a pneumatic signal that opens orcloses a latching valve, while supply air is used to apply or release aterminal device such as a spring brake.

To distinguish the characteristics of the present invention from currentstate of the art pneumatic systems, FIG. 1 provides a partial schematicrepresentation of a prior art air brake system 100 that utilizespneumatic circuits exclusively. In FIG. 1, all lines depicted in thedrawing are pneumatic lines with no electrical circuits being present.The dashboard module 110 includes five (5) pneumatic lines of ⅜ inchdiameter and several feet in length. These components are present in thevehicle's cab and traverse the firewall between the cab and the exteriorportion of the vehicle.

Primary reservoir air reservoir 120 and secondary air reservoir 122supply pressurized air to the parking control valve unit 112 by way ofsupply lines 120 a and 122 a. Dash valve 114 represents the “yellowbutton” as it is referred to by those skilled in the art, and includes acombination park pneumatic push-pull plunger. Dash valve 116 representsthe “red button” as it is referred to by those skilled in the art, andincludes a trailer park control and air supply pneumatic push-pullplunger. The pneumatic logic present in this system enables buttons 114and 116 to “pop” out automatically in the event the air reservoirs failand fall below a prescribed pressure, such as, for example, about 40 psifor valve 116 (red) and about 20 psi for valve 114 (yellow).

Delivery line 130 a supplies pressurized air to spring brake 190, whiletrailer supply line 130 b supplies pressurized air to tractor protectionmodule 140 and tractor protection valve 170. By way of primary deliveryline 150 a or secondary delivery line 150 b, foot brake valve 150delivers pressurized air to valve 170 directly or through double checkvalve 163. Likewise, trailer control valve 160 delivers pressurized airto valve 170 by way of delivery lines 160 a and 162. Tractor protectionvalve 170 may include a service line quick release valve and supply linequick release valve and delivers pressurized air to trailer supply line172 and trailer service line 174 as well as stop light switch 180 by wayof delivery line 180 a.

With reference to FIG. 2, an exemplary and generic embodiment ofelectro-pneumatic latching valve system 10 includes a switch unit 12, afirst electric control valve 18, a second electric control valve 26, anda pneumatic latching valve 40. A terminal device 50, and an airreservoir 60 are also included in the exemplary embodiment. The twooperational modes of the electric valves which may be solenoid valvesare null or closed, and energized or delivery. The pneumaticallylatching valve possesses the same two operational modes although itsinput is pneumatic pressure, not solenoid current. The description ofthe exemplary embodiment refers to the electric control valves assolenoid valves; however, other electrically controllable valves orpneumatic valves may be used to control the operation of thepneumatically latching valve including, but not limited to piezoelectricvalves and micro machine valves.

In FIG. 2, a series of electrical lines connects the switch unit to theelectric valves, and a plurality of pneumatic lines connects the airreservoir to the electric valves, the latching valve, and the terminaldevice. Pressurized air is delivered from reservoir 60 to the supplyports of valves 18 and 26 (see arrows B and F) and to the supply port ofpneumatic latching valve 40 (see arrow D). This “black air” remainsdeadheaded at these ports until the operator of the vehicle actuates oneof the switches in unit 12. Although not shown, an electronic controlunit (ECU) in the form of a printed circuit board or similar device maybe placed in-line between the switch unit and the solenoid assembliesfor the purposes of integrating additional functionality into thesystem.

In the exemplary embodiment shown in the Figures, terminal device 50 isa spring brake actuator that utilizes pressurized air to apply orrelease the parking brakes of a vehicle. With reference to FIG. 2, ifthe operator desires to release, i.e., deactivate, the parking brakes,release switch 14 is actuated. Upon actuation, electric current travelsfrom release switch 14 to release valve 20 (see arrow A). In response tothe electrical signal received at release valve 20, the delivery port ofsolenoid valve 22 is opened and pressurized air is delivered to the topcontrol port of pneumatic latching valve 40 (see arrow C). Uponreceiving this pneumatic signal, the piston within latching valve 40moves from its closed state and the supply port of valve 40 is openedallowing pressurized air to pass through to the delivery port of thevalve and into the spring brake, i.e., terminal device 50 (see arrow D).The pressurized air forces the spring within the brake chamber toretract and the vehicle's parking brakes are released allowing thevehicle to move.

When the operator releases switch 14, valve 22 closes and airflowthrough the valve ceases. Pressurized air that was delivered to thecontrol port of pneumatic latching valve 40 is exhausted through theexhaust port of solenoid valve 22. Although solenoid valve 22 is closed,and there is no air passing though the valve, the parking brakes of thevehicle remain released because pressurized supply air is still beingdelivered from reservoir 60 to the spring brake. Thus, valve 40 isreferred to as a pneumatic “latching” valve because continuous currentto the release valve is not required for the system to maintaincontinuous air flow to the terminal device. This aspect of the presentinvention is particularly advantageous over prior art systems becauseloss of electrical power or connectivity to the parking brake systemdoes not automatically result in the application of the vehicle'sparking brakes.

Again with reference to FIG. 2 if the operator desires to apply, i.e.,activate, the parking brakes, apply switch 16 is actuated. Uponactuation, electric current travels from apply switch 16 to apply valve28 (see arrow E). In response to the electrical signal received at applyvalve 28, the delivery port of solenoid valve 30 is opened andpressurized air is delivered to the bottom control port of pneumaticlatching valve 40 (see arrow G). Upon receiving this pneumatic signal,the piston within valve 40 returns to its closed state, terminating theflow of pressurized air through the valve to the delivery port and intothe spring brake, i.e., terminal device 50. The exhaust port ofpneumatic latching valve 40 then opens and air from the spring brakeactuator is exhausted to the atmosphere (see arrows H and I). Exhaustingthe pressurized air in this manner causes the spring within the brakechamber to return to its normal bias and the vehicle's parking brakesare applied.

When the operator releases switch 16, valve 30 closes and airflowthrough the valve ceases. Pressurized air that was delivered to thecontrol port of pneumatic latching valve 40 is exhausted through theexhaust port of solenoid valve 30. Although solenoid valve 30 is closed,and there is no air passing though the valve, the parking brakes of thevehicle remain applied because no pressurized air is being deliveredfrom reservoir 60 to the spring brake. As stated above, valve 40 isreferred to as a pneumatic latching valve because continuous current tothe apply solenoid is not required for the system to prevent air flow tothe terminal system device. Again, loss of electrical power orconnectivity to the parking brake system does not automatically resultin a change of state in the vehicle's parking brakes.

Electro-pneumatic latching valve system 10 may be incorporated intolarger, more complex tractor/trailer brake system. FIG. 3 provides apartial schematic of an exemplary embodiment of brake system 200. Thissystem comprises two basic modules or subsystems: driver interfacesubsystem 210 and brake control subsystem 245. Brake control subsystem245 further includes a remote module 250 and tractor protection module270. The components of driver interface subsystem 210 are typicallymounted on or within the dashboard of the vehicle, while remote module250 is typically mounted to an exterior surface of the cab of thevehicle and includes subcomponents that are both internal and externalto the cab. The tractor protection module 270 also typically includessubcomponents that are both internal to and external to the cab of thevehicle.

As shown in FIG. 3, driver interface system 210 comprises tractor andcombination park electrical switch unit (the “yellow button”) 212 andtrailer park and supply electrical switch unit (the “red button”) 214.In the exemplary embodiment, these buttons are 3-position, momentaryon-off-on, push-pull devices that provide the operator with an interfaceto the vehicle's parking system, and serve as the input devices to theoptional electronic control unit (see FIG. 5), which drives electricvalves 252, 254, 256, and 258, which in the exemplary embodiment aresolenoid valves. These buttons may be backlit for visibility and mayinclude a status indicator in the form of variable light intensity or anLED. The buttons are lit based either on input from pressure switches oron valve position, which typically includes contacting or non-contactingindicator switches that indicate whether the park brakes are applied orreleased.

A button coupling diode 216 is situated between assemblies 212 and 214and couples the function of the trailer and tractor components of thesystem. This coupling can be done with a diode or an equivalent devicesuch as an electrical driver circuit that emulates the logic of a diodeor may be implemented pneumatically with a check valve placed betweenthe park sides of the yellow and red valves. Typically, the couplinglogic utilized by a diode or other electronics is designed such thatoperating the park function of the yellow button unit automaticallyoperates the park function of the red button unit. This functionalitycan be characterized as a “single-button park feature.” Theelectro-pneumatic system of the present invention functions such that ifthe two status lights on the valve unit are extinguished, then a singlepull of the yellow button will pass current to both the yellow and redpark solenoids, thus lighting both the red and yellow buttons once theparking action is complete.

In the exemplary embodiment shown in FIG. 3, tractor brake circuit 213connects yellow button 212 to solenoid valve 256 and solenoid valve 258and provides an electrical pathway for activating these two solenoids.Likewise, trailer brake circuit 215 connects red button 214 to solenoidvalve 252 and solenoid valve 254 and provides an electrical pathway foractivating these two solenoids. It should be noted that in theembodiment that includes an electronic control unit circuits 213 and 215either connect the buttons to the electronic control unit or connect theelectronic control unit to the solenoids (see FIG. 5).

The power for operating circuits 213 and 215 is provided by a powersource 230, which is typically a 12V battery, and a capacitor 232 thatis in electrical communication with both driver interface subsystem 210and brake control subsystem 245. In the event of electrical power loss,capacitor 232 provides energy for at least one additional parkingapplication; thus, the operator may still park the vehicle despite theloss of electrical power to the brake system. A diode or other isolationcircuit may be employed to ensure that the capacitor's charge ispreserved only for the parking system, and not discharged through theremainder of the vehicle electrical system. In alternate embodiments, asimple capacitor, a complex capacitive circuit, or other suitable meansprovides backup power. In general, power supply 230 and capacitor 232comprise primary and secondary power supplies that provide the systemwith certain protections, conditioning, and backup emergency parkingcapability.

The embodiment shown in FIG. 5 includes a printed circuit board 211 thatserves as the electronic control unit for the brake system. The printedcircuit board can be placed in the vehicle's dash or it may be attachedto the parking control subsystem. In one embodiment, the brake controlsubsystem 245 is in an enclosure mounted on the back-of-cab wall, andprinted circuit board 211 is mounted on, attached to, or integrated withthe parking control subsystem. The printed circuit board may utilizedash buttons with hall effect sensors, and most or all of the supportcomponents or modules for the button unit, i.e., buttons 212 and 214,hall sensors, LEDs, LED intensity selection 221, LED drivers 222,feedback error detection 223, feedback sensors 224 and 225, solenoiddrivers 217, backup power supply 232, and interlock support/interface223, is integrated into the printed circuit board. The printed circuitboard may also include a microprocessor that includes an input handlermodule 219 and a logic circuit or module 218.

With reference to FIG. 3, an exemplary embodiment of remote module 250further comprises a plurality of electric valves (e.g., solenoidvalves), as well as two pneumatically latching valves. Although all fourelectric valves in the exemplary embodiment are basically identical,each solenoid performs a different function. These subcomponents may bemounted together within a single casting or molding. By way of example,each solenoid may be a 3-way/2-position normally closed solenoid valvethat pilots the pneumatic latch valve from one state to another based onthe operator's commands.

In the exemplary embodiment, “red” trailer supply valve 252 is situatedabove pneumatically latching trailer side valve 260 and “red” trailerpark solenoid 254 is situated below valve 260; however, these twosolenoids may be packaged together in a single housing and may reside ontop of or between the latching valves. This combination of solenoids andpneumatic latching valve comprise the portion of the system thatpneumatically operates the braking system of the vehicle's trailer (seeFIG. 3). Trailer supply line 264 exits pneumatically latching valve 260and provides pressurized air to tractor protection module 270 by way ofline 264 a. The trailer supply line feeds the trailer reservoirs andapplies or releases the parking and/or emergency brakes.

“Yellow” tractor park release solenoid valve 256 is situated abovepneumatically latching tractor side valve 262 and “yellow” tractor parkapply solenoid valve 258 is situated below pneumatically latching valve262; however, these two solenoids may be packaged together in a singlehousing and may reside on top of or between the latching valves. In theexemplary embodiment, this combination of solenoids and pneumaticallylatching valve comprise the portion of the system that pneumaticallyoperates spring brake 298, which is located in the tractor portion ofthe vehicle. Spring brake 298 is supplied with pressurized air bytractor spring brake delivery line 266.

In the embodiments shown in FIGS. 3 and 4, each pneumatic latching valveis operated by solenoid-piloted air rather than the operator's palm.Current commercially available valves would normally include a“mushroom” button that is manipulated, i.e., pushed in and pulled out bythe operator. Here the button has been removed, and the valves are“pushed in” or “pulled out” by pressurized control air from theelectrically controlled valves. In the exemplary embodiment, eachpneumatically latching valve “pops” automatically under a prescribed airpressure, such as, for example, about 40 psi for trailer brake actuator214 and about 20 psi for tractor brake actuator 212 regardless of thestate of the solenoids.

In the exemplary embodiment, this pressurized air is supplied to thesystem by primary air reservoir 240 and/or secondary air reservoir 242.Primary supply line 240 a, which runs from primary air reservoir 240,and secondary supply line 242 b, which runs from secondary air reservoir242 both connect to double check valve 243, which delivers the greaterof the two input pressures. Dual air supply line 244 exits double checkvalve 243 and then branches into multiple supply lines that provide thesolenoids and the pneumatically latching valves with pressurized controland supply air from supply line 244. As shown in FIG. 3, pneumaticallylatching valve 260 is supplied by supply line 244 a and pneumaticallylatching valve 262 is supplied by supply line 244 f. The solenoids aresupplied by supply lines 244 b and 244 d, which are further split intoadditional supply lines. Solenoid 252 is supplied by supply line 244 c,solenoid 254 is supplied by supply line 244 e, solenoid 256 is suppliedby supply line 244 g, and solenoid 258 is supplied by supply line 244 h.A dual air gauge (not shown) may be added to system 200 to monitor theair pressure within the pneumatic latch valves, which are the primaryoutputs of the system.

As shown in FIG. 3, an exemplary embodiment of tractor protection module270 includes two double check valves and a service line shut-off valve.Primary and secondary air reservoirs 240 and 242 supply pressurized airto foot brake valve 280, which is in communication with double checkvalve 294 by way of primary foot valve delivery line 281 a and secondaryfoot valve delivery line 281 b. Double check valve 294 is incommunication with a stop light switch (SLS) and also with double checkvalve 296 by way of delivery line 294 a. Primary and secondary airreservoirs 240 and 242 also supply pressurized air to trailer controlvalve 290, which is in communication with double check valve 296 by wayof trailer control delivery line 290 a. Double check valve 296 is incommunication with a stop light switch (SLS) and service line shut-offvalve by way of delivery line 296 a, which delivers to valve 297 thegreater of the air pressures received from foot brake valve 280 andtrailer control valve 290. Service line shut-off valve 297 deliverspressurized air to trailer service line 297 a and provides the tractorprotection function by closing the trailer service line in the eventthat the tractor supply reservoirs have failed or the trailer isotherwise damaged. The trailer service line pressure is proportional tothe braking being done by foot or by hand, and is used by the trailer toapply the proportional amount of service brakes for routine stopping ofthe vehicle.

As with the generic embodiment, when one or the other brake actuatorcontrol buttons (yellow and red buttons) is pushed in by the operator,electrical current flows to the solenoid valve located on top thepneumatic latching valve. The solenoid opens and delivers black orcontrol air to the piston within the pneumatic latching valve. Thepneumatically latching valve opens, delivering supply air to theterminal system component, e.g., the tractor spring brake. When thebrake actuator is released, the top solenoid valve closes and air flowthrough the solenoid valve ceases, and air delivered to the top of thepneumatically latching valve is exhausted. However, the valve remainsopen and continues to deliver supply air to the spring brake. When ayellow or red button is pulled outward from the neutral position, theabove-described process is reversed. Control air from the solenoid valveon the bottom of the pneumatically latching valve pushes the valve backto the closed position, thereby shutting off the air flow from supply todelivery, and exhausting pressurized air to atmosphere. Thus, aspreviously stated, even though the electrical power to the system mayfail, the pneumatic latching valve remains in its most recent state,i.e., it does not automatically apply the parking brakes due to anelectrical failure.

FIG. 4 provides a schematic representation of the present invention asapplied to an air brake system for a truck, bus, or non-towing vehicle.In this embodiment, brake system 200′ includes a driver interfacesubsystem 210′ and brake control subsystem 245′. Brake control subsystem245′ further includes a remote module 250′ and a spring brake 298′.Driver interface system 210′ comprises a single electrical switch 212′for energizing solenoids 256′ and 258′, which in turn controls theoperation of pneumatic latching valve 262′. Pressurized air is suppliedby primary reservoir 240′ and secondary reservoir 242′ and travelsthrough lines 240 a′ and 242 b′ to double check valve 243′. Pressurizedair is then delivered to the various system components by way ofpneumatic lines 244′, 244 b′, 244 j′, 244 f′, 244 g′, and 266′.

A number of variations are possible with the system of this invention.For example: (i) the solenoids may be assembled as a manifold at thevehicle's firewall such that all electrical connections are on thecab-side of the firewall and all the pneumatic connections are on theengine-side of the firewall; (ii) a time-delay circuit or strategy maybe employed such that risk of unintended actuation of the parking brakesis reduced; (iii) the actuators can be any working switch logic, eitherdriver-manipulated (push-pull buttons, flippers, sliders, dials) orcoupled to another system (transmission shifter “park” position, forexample); (iv) the system can receive additional logic, information, orcontrol from an ABS ECU with the authority to control the brake systemby a dedicated network protocol such as CAN; (v) the system may employ adedicated ECU or the system may receive only advisory information, notcommand information, from an engine or chassis ECU other than an ABSECU; (vi) the solenoid control may also be replaced by pneumatic pilotcontrol using pneumatic valves that would emulate the operation of the3-way/2-position, normally closed solenoids described above, e.g., theself-returning TH-3 (Bendix).

The present invention also provides a means for allowing safetyinterlocks to be integrated into a vehicle's brake system as simpleelectrical switch inputs. In general, the safety interlocks of thepresent invention (i) prohibit parking release based on informationobtained from devices around a vehicle that indicates a safety concernregarding movement of the vehicle and/or (ii) force the vehicle intopark based on information obtained from devices around a vehicle thatindicates the driver, upon exiting the vehicle, has forgotten to parkthe vehicle. In the exemplary embodiment, safety interlock and theftdeterrence are achieved simply by connecting existing vehicle switches(ignition key, brake light switch, door switch, safety belt switch,etc.) to an optional printed circuit board. The printed circuit board,if included, may be placed in an enclosure and may be located in thedash, integrated with existing buttons, or located on the in-the-cabside of the parking control subsystem.

In addition to air brake systems, the electro-pneumatic valve system ofthe present invention is compatible with any number of pneumatic systemsin which a change of state is not desirable should electric power to thesystem or its components be lost. For example, this electro-pneumaticvalve system may be used with a variety of pneumatic lift devices,including, but not limited to, powered doors, axle shifters, wheel chairlifts, cherry pickers, and air suspension systems.

While the above description contains many specificities, these shouldnot be construed as limitations on the scope of the invention, butrather as exemplification of certain preferred embodiments. Numerousother variations of the present invention are possible, and is notintended herein to mention all of the possible equivalent forms orramifications of this invention. Various changes may be made to thepresent invention without departing from the scope or spirit of theinvention.

What is claimed:
 1. An electro-pneumatic valve system, comprising: (a) afirst valve adapted to operatively respond to a momentary electricalsignal for opening the first valve, the first valve delivering a firstmomentary pneumatic control signal when open; (b) a second valve adaptedto operatively respond to a momentary electrical signal for opening thesecond valve, the second valve delivering a second momentary pneumaticcontrol signal when open; (c) a third valve in communication with thefirst and second valves, and wherein the third valve is adapted tooperatively respond to the first and second momentary pneumatic controlsignals, the third valve opening upon receiving the first momentarypneumatic control signal and remaining open until receiving the secondmomentary pneumatic control signal; (d) an electrical switch unit inelectrical communication with the first and second valves for sendingthe momentary electrical signals; (e) a source of pressurized controlair in communication with the first and second valves; (f) a source ofpressurized supply air in communication with the third valve, andwherein the pressurized supply air passes through the third valve whenthe valve is open; and (g) a terminal device in communication with thethird valve, and wherein the terminal device is adapted to receivepressurized supply air to release an associated parking brake when thethird valve is open and to exhaust pressurized supply air to apply theassociated parking brake when the third valve receives the secondmomentary pneumatic control signal and is closed.
 2. The system of claim1, further comprising an electrical control unit in electricalcommunication with the switch unit and the valves for controlling theoperation of the system.
 3. The system of claim 1, wherein the first andsecond valves are solenoid valves, piezoelectric valves, or micromachine valves.
 4. The system of claim 1, wherein the terminal device isa spring brake or pneumatic lift device.
 5. An electro-pneumatic systemfor controlling the parking and emergency brakes of a vehicle, whereinthe vehicle includes a truck portion, comprising: (a) a driverinterface, wherein the driver interface further comprises an electricalswitch unit for sending electrical signals; (b) a brake controlsubsystem in electrical communication with the driver interface, andwherein the brake control subsystem further comprises: (i) a first valveadapted to operatively respond to a momentary electrical signal foropening the first valve, the first valve delivering a first momentarypneumatic control signal when open; (ii) a second valve adapted tooperatively respond to a momentary electrical signal for opening thesecond valve, the second valve delivering a second momentary pneumaticcontrol signal when open; (iii) a third valve in communication with thefirst and second valves, and wherein the third valve is adapted tooperatively respond to the first and second momentary pneumatic controlsignals, the third valve opening upon receiving the first momentarypneumatic signal and remaining open until receiving the second momentarypneumatic signal; and (c) a source of pressurized control air incommunication with the first and second valves; (d) a source ofpressurized supply air in communication with the third valve, andwherein the pressurized supply air passes through the third valve whenthe valve is open; and (e) at least one spring brake in communicationwith the third valve for receiving and exhausting the pressurized supplyair, and wherein the spring brake is released to release the parkingbrake upon receiving the supply air in response to the third valvereceiving the first momentary pneumatic control signal; the spring brakeremaining released until the third valve receives the second momentarypneumatic control signal and exhausts the supply air.
 6. The system ofclaim 5, further comprising a primary electrical power supply inelectrical communication with the driver interface system.
 7. The systemof claim 5, further comprising a secondary electrical power supply inelectrical communication with the driver interface system.
 8. The systemof claim 5, wherein the first and second valves are solenoid valves.